Genetic and metabolic contributions of articular chondrocytes to degenerative joint disease and disturbed skeletal growth that cannot be readily studied using whole cartilage are approached by cell culture methods. Phenotypic glycosaminoglycan and collagen synthesis is expressed by cultured lapine articular chondrocytes under spinner although not monolayer conditions; the nature of the control of this expression is to be investigated. There are major species differences in the in vitro behavior of mammalian articular chondrocytes. Conditions for successful culture of human cells are being worked out. Human chondrocytes will be studied by cultural characteristics and by the above biochemical means according to strata within cartilage, age, osteoarthritis and such genetic disturbances as become available. Three inherited chondrodystrophies of rabbits are to be studied by comparable methods. Chondrocyte Growth Factor, a contaminant of pituitary glycoprotein hormone preparations, that has selective growth-promoting action on cultured articular chondrocytes, is being purified. The mechanism of its action will be further elaborated.